N, K = map(int, (input().split()))
S = input()
c = 0
x = 0
if S[K-1] == "(":
	while not x == 1:
		c += 1
		if S[K-1+c] == ")":
			x += 1
		else:
			x -= 1
	print(K+c)
else:
    while not x == 1:
        c += 1
        if S[K-1-c] == "(":
            x += 1
        else:
            x -= 1
    print(K-c)